1. Field of the Invention
The present invention relates to a battery protecting apparatus and a battery protecting circuit that includes a negative voltage terminal voltage detecting circuit that detects when the voltage of a negative voltage terminal decreases to less than a predetermined voltage, an abnormality detecting circuit that detects an abnormality in the charge/discharge conditions of a battery, and a switch that disconnects the connection between the battery and the negative voltage terminal when the negative voltage terminal voltage detecting circuit detects that the voltage of the negative voltage terminal has decreased to less than the predetermined voltage and when the abnormality detecting circuit detects an abnormality in the charge/discharge conditions of the battery.
2. Description of the Related Art
A rechargeable battery such as a lithium ion battery may be substantially degraded when it is under abnormal conditions such as overcharge, over discharge, and over current conditions. Therefore, such a rechargeable battery is usually protected from overcharge, over discharge, and over current by a battery protecting IC. Conventionally, detection of overcharge, over discharge, and/or over current conditions is delayed in order to avoid unnecessary abnormality detections.
However, in this case, the delay time increases the inspection time required for inspecting the protecting operations. Accordingly, the battery protecting IC preferably has a function of reducing such a delay time during inspection. In a conventional battery protecting IC, a dedicated pad (terminal) is provided for reducing the delay time during inspection, and the delay time is reduced by issuing commands to the dedicated pad during inspection so that the function of reducing the delay time may be activated. However, including such a dedicated pad leads to an increase in the chip area and cost increase.
In view of such circumstances, Japanese Laid-Open Patent Publication No. 2005-12852 discloses a battery protecting IC that reduces the inspection time without using a dedicated pad by activating the function of reducing the delay time when the potential of a negative voltage terminal is set to a negative potential that is not generated during normal operations.
However, in the case of activating the function of reducing the delay time when the potential of the negative voltage terminal is set to a negative potential that is not generated during normal operations in the battery protecting IC, for example, a function of detecting the connection of an overcharging charger between a positive voltage terminal and a negative voltage terminal may not be implemented when the potential of the negative voltage terminal is set to the negative potential.